WO2015008871A1 - Élément électroluminescent à semi-conducteurs à couche active de puits quantique et son procédé de fabrication - Google Patents

Élément électroluminescent à semi-conducteurs à couche active de puits quantique et son procédé de fabrication Download PDF

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Publication number
WO2015008871A1
WO2015008871A1 PCT/JP2014/069269 JP2014069269W WO2015008871A1 WO 2015008871 A1 WO2015008871 A1 WO 2015008871A1 JP 2014069269 W JP2014069269 W JP 2014069269W WO 2015008871 A1 WO2015008871 A1 WO 2015008871A1
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Prior art keywords
layer
light emitting
aigan
emitting element
semiconductor light
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PCT/JP2014/069269
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English (en)
Inventor
Shinji Saito
Rei Hashimoto
Jongil Hwang
Shinya Nunoue
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Kabushiki Kaisha Toshiba
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Publication of WO2015008871A1 publication Critical patent/WO2015008871A1/fr
Priority to US14/994,779 priority Critical patent/US9865770B2/en

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L33/00—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L33/02—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor bodies
    • H01L33/04—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor bodies with a quantum effect structure or superlattice, e.g. tunnel junction
    • H01L33/06—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor bodies with a quantum effect structure or superlattice, e.g. tunnel junction within the light emitting region, e.g. quantum confinement structure or tunnel barrier
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L33/00—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L33/0004—Devices characterised by their operation
    • H01L33/002—Devices characterised by their operation having heterojunctions or graded gap
    • H01L33/0025—Devices characterised by their operation having heterojunctions or graded gap comprising only AIIIBV compounds
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L33/00—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L33/005—Processes
    • H01L33/0062—Processes for devices with an active region comprising only III-V compounds
    • H01L33/0075—Processes for devices with an active region comprising only III-V compounds comprising nitride compounds
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L33/00—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L33/02—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor bodies
    • H01L33/26—Materials of the light emitting region
    • H01L33/30—Materials of the light emitting region containing only elements of Group III and Group V of the Periodic Table
    • H01L33/32—Materials of the light emitting region containing only elements of Group III and Group V of the Periodic Table containing nitrogen

Definitions

  • Embodiments described herein relate generally to a semico nductor light emitting element and a method for manufacturing t he same.
  • LEDs Light emitting diodes made from semiconductor light emitting elements using nitride semiconductor are used, for example, in display devices, lighting devices, and the like. In these semiconductor light emitting elements, high efficiency is required.
  • the embodiments of this invention provide an efficient semiconductor light emitting element and method for manufacturing the same.
  • a light emitting element includes an n-type semiconductor layer including a nitride semiconductor, a p-type semiconductor layer including a nitride semiconductor, and a light emitting unit.
  • the light emitting unit is provided between the n-type semiconductor layer and the p-type semiconductor layer, the light emitting unit emits light with a peak wavelength of not less than 530 nm.
  • the light emitting unit includes an n-side barrier layer and a first light emitting layer.
  • the first light emitting layer includes a first barrier layer provided between the n-side barrier layer and the p-type semiconductor layer, a first well layer contacting the n-side barrier layer between the n-side barrier layer and the first barrier layer, a first AIGaN layer provided between the first well layer and the first barrier layer and including Al x iGai -x iN (0.15 ⁇ xl ⁇ l), and a first p-side InGaN layer provided between the first AIGaN layer and the first barrier layer and including In ya iGai-yaiN (0 ⁇ yal ⁇ 0.1).
  • FIGS. 1A and IB are schematic cross-sectional views illu strating configurations of a semiconductor light emitting element according to a first embodiment.
  • FIG. 2 is a schematic cross-sectional view illustrating th e configuration of the semiconductor light emitting element acco rding to the first embodiment.
  • FIGS. 3A and 3B are schematic views illustrating the ch aracteristics of the semiconductor light emitting element accordin g to the first embodiment.
  • FIG. 4 is a graph showing the characteristics of a semic onductor light emitting element.
  • FIG. 5A and 5B are graphs showing the characteristics o f semiconductor light emitting elements.
  • FIG. 6 is a graph showing the characteristics of a semic onductor light emitting element.
  • FIG. 7 is a graph showing the characteristics of a semic onductor light emitting element.
  • FIG. 8 is a graph showing the characteristics of a semic onductor light emitting element.
  • FIGS. 9A to 9D are graphs showing the characteristics o f a semiconductor light emitting element according to the first e mbodiment.
  • FIG. 10 is a graph showing the characteristics of the s emiconductor light emitting element according to the first embod iment.
  • FIG. 11 is a graph showing the characteristics of the s emiconductor light emitting element according to the first embod iment.
  • FIG. 12 is a flowchart illustrating a manufacturing met hod of a semiconductor light emitting element according to the s econd embodiment.
  • FIG. 13A and FIG. 13B are schematic views illustrating a semiconductor light emitting element according to a third em bodiment.
  • FIGS. 14A to 14F are schematic views illustrating the s emiconductor light emitting element according to the embodimen t.
  • FIG. 15 is a graph showing the characteristics of semic onductor light emitting elements.
  • FIG. 16 is a graph showing the characteristics of a se miconductor light emitting element.
  • FIGS. 1A and IB are schematic cross-sectional views illustrating configurations of a semiconductor light emitting element according to a first embodiment.
  • a semiconductor light emitting element 110 includes an n-type semiconductor layer 10, a p-type semiconductor layer 20, and a light emitting unit 30.
  • the n-type semiconductor layer 10 and the p-type semiconductor layer 20 include nitride semiconductors.
  • the light emitting unit 30 is provided between the n-type semiconductor layer 10 and the p-type semiconductor layer 20.
  • the light emitting unit 30 includes an n-side barrier layer BLN, and a first light emitting layer ELI.
  • the first light emitting layer ELI is provided between the n-side barrier layer BLN and the p-type semiconductor layer 20. >
  • the direction from the n-type semiconductor layer 10 toward the p-type semiconductor layer 20 is defined as the "Z-axis direction"
  • the first light emitting layer ELI includes a first barrier layer BL1, a first well layer WL1, a first AIGaN layer ML1, and a first p- side InGaN layer CLal.
  • the first barrier layer BL1 is provided between the n-side barrier layer BLN and the p-type semiconductor layer 20.
  • the first well layer WL1 is in contact with the n-side barrier layer BLN between the n-side barrier layer BLN and the first barrier layer BL1.
  • the first AIGaN layer ML1 is provided between the first well layer WL1 and the first barrier layer BL1, and includes Al x iGai- x iN (0.15 ⁇ xl ⁇ l).
  • the first p-side InGaN layer CLal is provided between the first AIGaN layer ML1 and the first barrier layer BL1, and includes In ya iGai-yai (0 ⁇ yal ⁇ 0.1).
  • the number of well layers WL in the semiconductor light emitting element 110 is 1. In this way, the light emitting unit 30 can have a single quantum well (SQW) configuration.
  • SQL single quantum well
  • the light emitting unit 30 further includes a second light emitting layer EL2.
  • the second light emitting layer EL2 includes, for example, a second barrier layer BL2, a second well layer WL2, a second AIGaN layer ML2, and a second p-side InGaN layer CLa2.
  • the second well layer WL2 is provided between the first well layer WL1 and the n-type semiconductor layer 10.
  • the second barrier layer BL2 is in contact with the first well layer WL1 between the first well layer WL1 and the second well layer WL2.
  • the second AIGaN layer ML2 is provided between the second well layer WL2 and the second barrier layer BL2, and includes Al x2 Gai- X 2N (0.15 ⁇ x2 ⁇ l).
  • the second p-side InGaN layer CLa2 is provided between the second AIGaN layer ML2 and the second barrier layer BL2, and includes In y a 2 Gai -y a2N (0 ⁇ ya2 ⁇ l).
  • the semiconductor light emitting element 111 a plurality of well layers WL is provided.
  • the light emitting unit 30 can have a multiple quantum well (MQW) configuration.
  • the number of well layers WL is, for example, 4.
  • the number of light emitting layers EL is 4.
  • the light emitting unit 30 includes, for example, a plurality of light emitting layers EL (first light emitting layer ELI to nth light emitting layer ELn).
  • n is an integer of 2 or greater.
  • the (i-(- l)-th light emitting layer EL(i+ l) is provided between the i-th light emitting layer ELi and the n-type semiconductor layer 10.
  • "i" is an integer of 1 or greater.
  • the i-th light emitting layer ELi includes an i-th barrier layer BLi, an i-th well layer WLi, an i-th AIGaN layer MLi, and an i-th p- side InGaN layer CLai.
  • the (i+ l)-th well layer WL(i+ l ) is provided between the i-th well layer WLi and the n-type semiconductor layer 10.
  • the (i+ 1)- th barrier layer BL(i+ l) is in contact with the i-th well layer WLi between the i-th well layer WLi and the (i+ l)-th well layer WL(i+ l).
  • the (i+ l )-th AIGaN layer M L(i+ l ) is provided between the (i+ l)-th well layer WL(i+ l) and the (i+ l)-th barrier layer BL(i+ l ), and includes AI X ( i+ i)Gai -X (i + i)N (0.15 ⁇ x(i+ l) ⁇ 1) .
  • the (i+ l)-th p-side InGaN layer CLa(i+ l) is provided between the (i+ l)-th AIGa N layer ML(i+ l) and the (i+ l)-th barrier layer BL(i+ l), and includes In y a(i+i)Gai. y (i + 1 )N (0 ⁇ ya(i+ l) ⁇ 0. 1) .
  • the first to nth barrier layers BL1 to BLn are sometimes collectively referred to as the barrier layer BL.
  • the first to nth well layers WLI to WLn are sometimes collectively referred to as the well layer WL.
  • the first to nth AIGaN layers ML1 to MLn are sometimes collectively referred to as the AIGaN layer ML.
  • the first to nth p-side InGa N layers CLa l to CLan are sometimes collectively referred to as the p-side InGaN layer CLa .
  • the Al composition ratios may be the same as each other, or may be different from each other.
  • the Al composition ratio x is set to 0. 15 ⁇ x ⁇ l .
  • the Al composition ratio x (Al composition ratio within group-Ill) is, for example, not less than 0.25.
  • the Al composition ratio x is, for example, not less than 0.3.
  • the Al composition ratio in the plurality of AIGaN layers ML is the same (Al composition ratio x is constant) .
  • the thicknesses of the plurality of AIGaN layers ML may be the same as each other, or they may be different from each other. In any AIGaN layer M L, the thickness is set to, for example, 1 atomic layer or more and not more than 2 nm .
  • the band gap energy of the i-th well layer WLi is smaller than the band gap energy of the i-th barrier layer BLi, and smaller than the band gap energy of the n-side barrier layer BLN.
  • an InGaN layer is used for the well layer WL
  • a GaN layer is used for the barrier layer BL.
  • the In composition ratio (In composition ratio in group-Ill) in the barrier layer BL is lower than the In composition ratio in the well layer WL.
  • the In composition ratio in the well layer WL is determined in accordance with the target wavelength of the light to be emitted.
  • the In composition ratio in the well layer WL is, for example, not less than 0.2 and not more than 0.6.
  • the In composition ratios may be the same as each other, or they may be different from each other.
  • the In composition ratio ya is set to 0 ⁇ ya ⁇ 0.1.
  • the In composition ratio ya is, for example, lower than the In composition ratio in the well layer WL.
  • the In composition ratio ya is, for example, not less than 0.002 and not more than 0.05.
  • the In composition ratio ya is, for example, not less than 0.003 and not more than 0.03.
  • the In composition ratios in the plurality of p-side InGaN layers CLa are the same (In composition ratio ya is constant). In the plurality of p-side InGaN layers CLa, the In composition ratio is lower than the In composition ratio in the well layer WL.
  • each of the plurality of p-side InGaN layers CLa may be the same as each other, or they may be different from each other.
  • the thickness is set to, for example, 1 atomic layer or more and not more than 2 nm.
  • the thickness of the p-side InGaN layer CLa is preferably, for example, less than 2 nm.
  • the thickness of the well layer WL is, for example, not less than 1.0 nanometer (nm) and not more than 5.0 nm.
  • the thickness of the well layer WL is less than 1.0 nm, it is difficult to obtain light emission with wavelengths longer than 530 nm.
  • the thickness of the well layer WL is greater than 5.0 nm, degradation of crystal quality can easily occur.
  • the spatial separation of the wave functions of electrons and electron holes becomes larger, and the luminous intensity tends to become weaker.
  • the thickness of the barrier layer BL is, for example, not less than 3 nm and not more than 50 nm.
  • the thickness of the barrier layer BL is less than 3 nm, the wave functions between different well layers WL interfere, due to the narrowing of the gaps between the plurality of well layers WL.
  • the thickness of the barrier layer BL is not less than 3 nm, the interference of the wave functions in the well layers WL is suppressed.
  • the thickness of the barrier layer BL is greater than 50 nm, the thickness of the light emitting layer EL becomes too thick, and the operating voltage increases.
  • the first light emitting layer ELI further includes, for example, a first n-side InGaN layer CLbl, a first p-side nitride including layer DLal, and a first n-side nitride including layer DLbl.
  • the first light emitting layer ELI further includes a first intermediate layer SL1.
  • the i-th light emitting layer ELi further includes an i-th n-side InGaN layer CLbi, an i-th p-side nitride including layer DLai, an i-th n-side nitride including layer DLbi, and a i-th intermediate layer SLi.
  • the first to nth n-side InGaN layer CLbl to CLbn are sometimes collectively referred to as the n-side InGaN layer CLb.
  • the first to nth p-side nitride including layer DLal to DLan are sometimes collectively referred to as the p-side nitride including layer DLa.
  • the first to nth n-side nitride including layer DLbl to DLbn are sometimes collectively referred to as the n-side nitride including layer DLb.
  • the first to nth Intermediate layer SL1 to SLn are sometimes collectively referred to as the intermediate layer SL.
  • the p-side InGaN layer CLa and the n-side InGaN layer CLb are sometimes collectively referred to as the InGaN layer CL.
  • the p-side nitride including layer DLa and the n-side nitride including layer DLb are sometimes collectively referred to as the nitride including layer DL.
  • the n-side InGaN layer CLb is provided between the p-side
  • InGaN layer CLa and the AIGaN layer ML includes Iny b Gai -y bN (0 ⁇ yb ⁇ 0.1).
  • the In composition ratio yb in the n-side InGaN layer CLb is, for example, lower than the In composition ratio in the well layer WL.
  • the In composition ratios may be the same as each other, or may be different from each other.
  • the In composition ratio of the n-side InGaN layer CLb may be the same as the In composition ratio of the p-side InGaN layer CLa, or it may be different.
  • the In composition ratio yb is set to 0 ⁇ yb ⁇ 0.1.
  • the In composition ratio ya is, for example, not less than 0.002 and not more than 0.05.
  • the In composition ratio yb is, for example, not less than 0.003 and not more than 0.03.
  • the In composition ratio in the plurality of n-side InGaN layers CLb is the same (In composition ratio yb is constant), and is the same as the In composition ratio of the p-side InGaN layer CLa.
  • the In composition ratio is lower than the In composition ratio in the well layer WL.
  • the p-side nitride including layer DLa is provided between the p-side InGaN layer CLa and the n-side InGaN layer CLb, and includes In Z aGai -za N (0 ⁇ za ⁇ ya, 0 ⁇ za ⁇ yb).
  • the n-side nitride including layer DLb is, for example, provided between the n-side InGaN layer CLb and the AIGaN layer ML, and includes In zb Gai -Z bN (0 ⁇ zb ⁇ ya, 0 ⁇ zb ⁇ yb).
  • the p-side nitride including layer DLa does not include In.
  • the p-side nitride including layer DLa for example, is GaN.
  • the n-side nitride including layer DLb for example, does not include In.
  • the n-side nitride including layer DLb for example, is GaN.
  • the intermediate layer SL is, for example, provided between the well layer WL and the AIGaN layer ML.
  • the thickness of the intermediate layer SL is, for example, not more than 1 nm.
  • the thickness of the intermediate layer SL is, for example, 0.5 nm.
  • the intermediate layer SL may not be provided.
  • the AIGaN layer ML may be provided in contact with the well layer WL.
  • the light emitting layer EL for example the p-side InGaN layer CLa and the AIGaN layer ML may be in contact.
  • the light emitting layer EL does not include the p-side nitride including layer DLa, the n-side nitride including layer DLb, and the n-side InGaN layer CLb.
  • InGaN which has a long growth time, does not grow, so the growth time of the light emitting layer EL is short.
  • the n-side InGaN layer CLb and the AIGaN layer ML may be in contact.
  • the light emitting layer EL does not include, for example, the n- side nitride including layer DLb. In this way, the growth time can be shortened. Also, it is also possible to suppress removal of Al due to the time for switching the source gas.
  • FIG. 2 is a schematic cross-sectional view illustrating the configuration of the semiconductor light emitting element according to the first embodiment.
  • the semiconductor light emitting element 110 semiconductor light emitting element 111 according to this embodiment further includes a substrate 60, a buffer layer 50, an n-side electrode 70, and a p-side electrode 80.
  • the n-type semiconductor layer 10 is provided between the substrate 60 and a light emitting unit 30.
  • the buffer layer 50 is, for example, provided between the substrate 60 and the n-type semiconductor layer 10.
  • Sapphire for example, is used for the substrate 60.
  • a sapphire (0001) substrate is used for the substrate 60.
  • a SiC substrate, a Si substrate, or a GaN substrate may be used for the substrate 60.
  • a GaN layer for example, is used for the buffer layer 50.
  • the n-type semiconductor layer 10, the light emitting unit 30, and the p-type semiconductor layer 20 are formed in that order on the buffer layer 50.
  • the substrate 60 and the buffer layer 50 are provided when necessary, and may be omitted. After forming the semiconductor layers as described above on the buffer layer 50, the substrate 60 may be removed.
  • the n-type semiconductor layer 10 includes, for example, a first major surface 10a and a second major surface 10b.
  • the first major surface 10a is, for example, the surface on the light emitting unit 30 side.
  • the second major surface 10b is the surface on the opposite side to the first major surface 10a.
  • n-side electrode 70 is electrically connected to the n-type semiconductor layer 10 in the portion where the n-type semiconductor layer 10 is exposed.
  • the n-side electrode 70 is, for example, disposed on the first major surface 10a side of the n-type semiconductor layer 10.
  • the n-type semiconductor layer 10 includes a first portion lOp and a second portion lOq.
  • the second portion lOq is aligned with the first portion lOp in a direction that intersects the Z-axis direction.
  • the p-type semiconductor layer 20 is separated from the first portion lOp in the pZ-axis direction.
  • the light emitting unit 30 is disposed between the first portion lOp and the p-type semiconductor layer 20.
  • the p-side electrode 80 is disposed, for example, on the p- type semiconductor layer 20.
  • the state of being provided on includes, in addition to the state of being directly provided on, the state in which another layer is inserted between the two.
  • the p-side electrode 80 includes a first p- side electrode portion 81 and a second p-side electrode portion 82.
  • the second p-side electrode portion 82 is provided between the first p-side electrode portion 81 and the p-type semiconductor layer 20.
  • the p-type semiconductor layer 20 includes a first p-type layer 21 and a second p-type layer 22.
  • the second p-type layer 22 is provided between the first p-type layer 21 and the light emitting unit 30.
  • a voltage is applied between the n-side electrode 70 and the p-side electrode 80, a current is supplied to the light emitting unit 30 via the n-type semiconductor layer 10 and the p- type semiconductor layer 20. Light is emitted from the light emitting unit 30.
  • the peak wavelength ⁇ of the light (luminescent light) emitted from the light emitting unit 30 is, for example, not less than 530 nanometers (nm). In another example, the peak wavelength ⁇ of the luminescent light is, for example, not less than 530 nm and less than 570 nm. In another example, the peak wavelength ⁇ of the luminescent light is, for example, not less than 570 nm and less than 600 nm. In another example, the peak wavelength ⁇ of the luminescent light is, for example, not less than 600 nm and not more than 750 nm.
  • a sapphire (0001) substrate 60 is thermally cleaned at a susceptor temperature of 1100°C.
  • the susceptor temperature is lowered to 500°C, and a buffer film that will serve as the buffer layer 50 is grown on the substrate 60.
  • the buffer film is, for example, a GaN film.
  • the susceptor temperature is raised to, for example, 1120°C, and an n-type semiconductor film that will serve as the n-type semiconductor layer 10 is formed on the buffer film.
  • the n-type semiconductor film is, for example, an n-type GaN film doped with Si.
  • n-side barrier film that will serve as the n-side barrier layer BLN is formed on the n-type semiconductor film.
  • the n-side barrier film is, for example, GaN doped with Si.
  • the thickness of the n-side barrier film (n-side barrier layer BLN) is, for example, not less than 1 nm and not more than 50 nm, for example, 12.5 nm.
  • the susceptor temperature is reduced to within the range of not less than 700°C and not more than 800°C, and a first well film that will serve as the first well layer WL1 is formed.
  • the first well film is, for example, an InGaN film.
  • the thickness of the first well film (first well layer WLl) is, for example, approximately 3 nm.
  • the In composition ratio of the first well layer WLl is, for example, approximately 0.23.
  • a first intermediate film that will serve as the first intermediate layer SLl is formed on the first well layer WLl.
  • the forming temperature of the first intermediate film (first intermediate layer SLl) is, for example, the same as the forming temperature of the first well layer WLl.
  • the first intermediate film is, for example, a GaN film.
  • the thickness of the first intermediate film is, for example, 0.5 nm.
  • the susceptor temperature is raised to, for example, 890°C, and a first AIGaN film that will serve as the first AIGaN layer ML1 is formed.
  • the thickness of the first AIGaN film (first AIGaN layer ML1) is, for example, 1 nm.
  • the Al composition ratio of the first AIGaN layer ML1 is, for example, 0.3.
  • a first n-side nitride containing film that will serve as the first n-side nitride including layer DLbl is formed on the first AIGaN layer ML1.
  • the first n-side nitride including layer DLbl is, for example, GaN.
  • the thickness of the first n-side nitride including layer DLbl is, for example 1 nm.
  • a first n-side InGaN film that will serve as the first n-side InGaN layer CLbl is formed on the first n-side nitride including layer DLbl.
  • the thickness of the first n-side InGaN film (first n-side InGaN layer CLbl) is, for example, 1 nm.
  • the In composition ratio yb of the first n-side InGaN layer CLbl is, for example, 0.01.
  • a first p-side nitride containing film that will serve as the first p-side nitride including layer DLal is formed on the first n-side InGaN layer CLbl.
  • the first p-side nitride including layer DLal is, for example, GaN.
  • the thickness of the first p-side nitride including layer DLal is, for example, 1 nm.
  • a first p-side InGaN film that will serve as the first p-side InGaN layer CLal is formed on the first p-side nitride including layer DLal.
  • the thickness of the first p-side InGaN film (first p- side InGaN layer CLal) is, for example 1 nm.
  • the In composition ratio ya of the first p-side InGaN layer CLal is, for example, 0.01.
  • the forming temperatures of the first n-side InGaN layer CLbl and the first p-side InGaN layer CLal are, for example, greater than 810°C and less than 905°C. For example, not less than 860°C and not more than 890°C.
  • the forming temperature is the same as the forming temperature of the first AIGaN layer ML1.
  • the forming temperature of the first n-side nitride including layer DLbl and the first p-side nitride including layer DLal is the same as the forming temperature of the first n-side InGaN layer CLbl and the first p-side InGaN layer CLal.
  • a first barrier film that will serve as the first barrier layer BL1 is formed on the first p-side InGaN layer CLal.
  • the first barrier film is, for example, GaN.
  • the thickness of the first barrier film (first barrier layer BL1) is, for example, thicker than that of the first intermediate layer SL1, the first p-side nitride including layer DLal, and the first n-side nitride including layer DLbl.
  • the thickness of the first barrier film (first barrier layer BL1) is, for example, 4 nm.
  • the forming temperature of the first barrier layer BL is, for example, 890°C.
  • the first light emitting layer ELI is formed.
  • the second light emitting layer EL2 to the fourth light emitting layer EL4 are formed in the same way as described above
  • the light emitting unit 30 is formed.
  • the p-type semiconductor layer 20, for example, is formed on the light emitting unit 30.
  • a second p-type film that will serve as the second p-type layer 22 is formed on the light emitting unit 30.
  • the second p-type film (second p-type layer 22) is, for example, GaN doped with Mg to a second concentration.
  • a first p-type film that will serve as the first p-type layer 21 is formed on the second p-type layer 22.
  • the first p-type film (first p-type layer 21) is, for example, GaN doped with Mg to a first concentration.
  • the first concentration is, for example, higher than the second concentration.
  • the forming temperature of the second p-type layer 22 is, for example, 910°C.
  • the thickness of the first p-type layer 21 is, for example, 80 nm.
  • the forming temperature of the first p-type layer 21 is, for example, 910°C.
  • the thickness of the first p-type layer 21 is, for example, 30 nm.
  • the p-type semiconductor layer 20 is formed.
  • Each of these layers can be grown using, for example, the metal organic chemical vapor deposition method (MOCVD), and the metal organic vapor phase epitaxy method (MOVPE), or the like.
  • MOCVD metal organic chemical vapor deposition method
  • MOVPE metal organic vapor phase epitaxy method
  • the following can be used as the materials when forming each of the semiconductor layers.
  • trimethylgallium (TMGa), triethylgallium (TEGa), and the like can be used as the raw material for Ga.
  • trimethylindium (TMIn), triethylindium (TEIn), and the like can be used as the raw material for In.
  • trimethyl aluminum (TMAI) and the like can be used as the raw material for Al.
  • ammonia (NH 3 ), mono methyl hydrazine (MMHy), di methyl hydrazine (DMHy) and the like can be used as the raw material for N.
  • mono silane (SiH 4 ) and the like can be used as the raw material for Si.
  • biscyclopentadienyl magnesium (Cp 2 Mg) and the like can be used as the raw material for Mg.
  • n-side electrode 70 is formed on the exposed n-type semiconductor layer 10.
  • an electron beam deposition method can be used for forming the n-side electrode 70.
  • Ti/Pt/Au can be used for the n-side electrode 70.
  • the p-side electrode 80 is formed on the p-type semiconductor layer 20.
  • a second p-side electrode film that will serve as the second p-side electrode portion 82 is formed on the p-type semiconductor layer 20.
  • the sputtering method can be used for forming the second p-side electrode.
  • the second p-side electrode portion 82 is, for example, an electrode with optical transparency.
  • the second p-side electrode portion 82 includes, for example, an oxide that includes at least any element selected from the group consisting of In, Sn, Ga, and Ni.
  • ITO Indium Tin Oxide
  • a thin metal film with optical transparency may be used.
  • the first p-side electrode portion 81 is formed on the second p-side electrode portion 82.
  • the electron beam deposition method can be used for forming the first p-side electrode film.
  • Ti/Pt/Au can be used for forming the first p-side electrode portion 81.
  • the semiconductor light emitting element 111 is formed.
  • the following is a description of an example of the band structure of the light emitting layer EL of the semiconductor light emitting element 111.
  • FIGS. 3A and 3B are schematic views illustrating the characteristics of the semiconductor light emitting element according to the first embodiment.
  • FIG. 3A illustrates an example of the energy band diagram of the first light emitting layer ELI in the semiconductor light emitting element 110 (or the semiconductor light emitting element 111).
  • the horizontal axis represents the band gap energy Eg.
  • the vertical axis represents the stacking direction (Z-axis direction) of the first light emitting layer ELI.
  • FIG. 3B is a transmission electron microscope photographic image of the first light emitting layer ELI.
  • FIG. 3B is an image of the cross-section of the semiconductor light emitting element 110 (or the semiconductor light emitting element 111).
  • the band gap energy Eg of the first well layer WL1 is low.
  • the band gap energy Eg of the first AIGaN layer ML1 is high.
  • the band gap energy Eg of the n-side barrier layer BLN and the first barrier layer BL1 is higher than that of the first well layer WL1, and lower than that of the first AIGaN layer ML1.
  • the band gap energy Eg of the first p-side InGaN layer CLal and the first n-side InGaN layer CLb is higher than that of the first well layer WL1, and lower than that of the first barrier layer BL1.
  • the band gap energy Eg of the first p-side nitride including layer DLal, the first n-side nitride including layer DLbl, and the first intermediate layer SLl is higher than that of the first well layer WL1, and lower than that of the first AIGaN layer ML1.
  • the well layer WL, the AIGaN layer ML, the n-side InGaN layer CLb, and the p-side InGaN layer CLa are aligned in that order.
  • the intermediate layer SL is provided between the well layer WL and the AIGaN layer ML.
  • the reside nitride including layer DLb is provided between the AIGaN layer ML and the n-side InGaN layer CLb.
  • the p-side nitride including layer DLa is provided between the n-side InGaN layer CLb and the p-side InGaN layer CLa.
  • the efficiency of the semiconductor light emitting element 110 is high.
  • FIG. 4 is a graph showing the characteristics of a semiconductor light emitting element.
  • the horizontal axis is the peak wavelength ⁇ (nm), and the vertical axis is the optical output OP.
  • the optical output OP is the relative value of the light output when a current of 20 mA is flowing.
  • data is shown for semiconductor light emitting elements 119a and 119b according to reference examples, in addition to semiconductor light emitting elements 111a and 111b according to this embodiment.
  • the forming temperature of the first p-side InGaN layer CLal and the first n-side InGaN layer CLbl of the first light emitting layer ELI was 840°C.
  • the second light emitting layer EL2 to the fourth light emitting layer EL4 was the same as the configuration of the semiconductor light emitting element 111.
  • the forming temperature of the first p-side InGaN layer CLal, and the first n-side InGaN layer CLbl of the first light emitting layer ELI was 890°C.
  • the configuration of the semiconductor light emitting element 111b was the same as the configuration of the semiconductor light emitting element 111.
  • each light emitting layer EL of this semiconductor light emitting element 119a included the well layer WL and the barrier layer BL. In other words, the light emitting layer EL did not include the AIGaN layer ML and the InGaN layer. Apart from this, the configuration of the semiconductor light emitting element 119a was the same as the configuration of the semiconductor light emitting element 111.
  • Each light emitting layer EL of the semiconductor light emitting element 119b included the well layer WL, the AIGaN layer ML, and the barrier layer BL. In other words, the light emitting layer EL did not include the InGaN layer CL. Apart from this, the configuration of the semiconductor light emitting element 119b was the same as the configuration of the semiconductor light emitting element 111.
  • the optical output OP reduces for the semiconductor light emitting elements 111a and 111b and for the semiconductor light emitting elements 119a and 119b of the reference example.
  • the optical output OP is significantly reduced.
  • the optical output OP is higher than that of the semiconductor light emitting element 119a. This is because, for example, the reduction in luminous efficiency due to the quantum confined Stark effect is suppressed by providing the AIGaN layer ML in the light emitting layer EL. This effect is significant when, for example, the peak wavelength ⁇ is not less than 520 nm.
  • the light emitting layer EL includes the AIGaN layer ML and the InGaN layer.
  • the optical output OP of the semiconductor light emitting elements 111a and 111b is even higher than the optical output OP of the semiconductor light emitting element 119b. In other words, efficiency is high. This effect is particularly significant when, for example, the peak wavelength ⁇ is not less than 530 nm.
  • the reason that high optical output OP can be obtained in the semiconductor light emitting elements Ilia and 111b according to this embodiment is considered to be as follows.
  • the lattice spacing of the well layer WL is wide compared with the other layers, so strain occurs, and a piezo electric field is generated.
  • the integrated value of the overlap in the electron hole wave function and the electron wave function is reduced, so the luminous efficiency is reduced.
  • large strain occurs, so this tendency is significant.
  • the reduction in luminous efficiency due to the quantum confined Stark effect as described above is suppressed.
  • a layer that includes Al is provided in the light emitting layer EL (for example, AIGaN layer ML)
  • strain is introduced and piezo electric fields are easily generated.
  • the Al composition ratio xl in the first AIGaN layer ML1 it is effective to increase the Al composition ratio xl in the first AIGaN layer ML1 to, for example, not less than 0.15.
  • a large strain is induced in the well layer WL1.
  • the next layer for example, the second well layer WL2 of the second light emitting layer EL2 is grown while this strain remains, misfit dislocations are generated in the second well layer WL2.
  • the first p-side InGaN layer CLal is provided within the first light emitting layer ELI.
  • the misfit dislocations are generated within the first p-side InGaN layer CLal, for example.
  • the average In composition within the light emitting layer EL is designed to be low.
  • the semiconductor light emitting element according to this embodiment by providing a layer that includes In within the light emitting layer EL, it is possible to obtain high efficiency, even though the average In composition ratio increases.
  • the forming temperature of the p-side InGaN layer CLa and the n-side InGaN layer CLb is set to, for example, not less than 860°C and not more than 890°C, it is possible to obtain higher efficiency. This is considered to be because, for example, the supply of raw material atoms to the surface during growth is made more uniform.
  • each of the light emitting layers EL includes two thin InGaN layers CL (p-side InGaN layer CLa and n-side InGaN layer CLb), and two nitride including layers DL (p-side nitride including layer DLa).
  • Each light emitting layer EL may also include one InGaN layer CL.
  • the number of InGaN layers CL and nitride including layers DL in each light emitting layer EL is large, and if the thickness of each light emitting layer EL becomes too thick, the average In composition becomes larger, and, on the contrary, the efficiency can be reduced.
  • the number of InGaN layers CL included in each light emitting layer EL is, for example, about two.
  • a first distance dl between the first p- side InGaN layer CLal and the first n-side InGaN layer CLbl and the first well layer WL1 is, for example, longer than a second distance d2 between the first p-side InGaN layer CLal and the first n-side InGaN layer CLbl and the second well layer WL2.
  • the first distance dl may also be shorter than the second distance d2.
  • the first distance dl may be the same as the second distance d2.
  • the first distance dl and the second distance d2 main, for example, be determined by the thickness of each layer (first intermediate layer SL1, first AIGaN layer ML1, first n-side nitride including layer DLbl, first n-side InGaN layer CLbl, first p-side nitride including layer DLal, first p-side InGaN layer CLal, first barrier layer BL1). Examples of the thicknesses of each of these layers are described later.
  • all of the first light emitting layer ELI to the fourth light emitting layer EL4 include the AIGaN layer ML and the InGaN layer CL.
  • the light emitting unit 30 includes a plurality of light emitting layers EL, the AIGaN layer ML and the InGaN layer CL are provided in at least one light emitting layer EL.
  • the light emitting layer EL located close to the p-type semiconductor layer 20 is provided with the AIGaN layer ML and the InGaN layer CL.
  • the above effect can be obtained, so high efficiency can be easily obtained.
  • FIG. 5A and 5B are graphs showing the characteristics of semiconductor light emitting elements.
  • FIG. 5A shows the efficiency Eff of the semiconductor light emitting element 111b according to this embodiment and the semiconductor light emitting element 119a according to a reference example.
  • the horizontal axis is current (mA).
  • the vertical axis is the relative luminous efficiency Eff at a wavelength of 550 nm.
  • FIG. 5B shows the efficiency Eff of the semiconductor light emitting element 111b according to this embodiment and the semiconductor light emitting element 119b according to a reference example.
  • the horizontal axis is current (mA).
  • the vertical axis is the relative optical output OP (at the wavelength of 550 nm).
  • the relative luminous efficiency Eff and the relative optical output OP are higher than for the semiconductor light emitting element 119b.
  • FIG. 6 is a graph showing the characteristics of a semiconductor light emitting element.
  • FIG. 6 shows the relative EL intensity when the thickness dML of the AIGaN layer ML is varied.
  • the horizontal axis is the thickness dML (nm) of the AIGaN layer ML.
  • the vertical axis is the relative EL intensity Intl at the wavelength of 550 nm.
  • data is shown for a semiconductor light emitting element 119c according to a reference example, in addition to data for semiconductor light emitting elements 112a and 112b according to this embodiment.
  • the Al composition ratio x of the AIGaN layer ML included in the light emitting layer EL of the semiconductor light emitting element 112a is 0.3.
  • the configuration of the semiconductor light emitting element 112b is the same as that of the semiconductor light emitting element 112a, except that the Al composition ratio x of each of the AIGaN layers ML is 0.15.
  • the configuration of the semiconductor light emitting element 119c is the same as that of the semiconductor light emitting element 112a, except that the Al composition ratio x of each of the AIGaN layers ML is 0.
  • the relative EL intensity of the light emitting layer EL is high when the AIGaN layer ML is included.
  • FIG. 7 is a graph showing the characteristics of a semiconductor light emitting element.
  • the relative EL intensity is shown when the thickness dCL of each InGaN layer CL is varied.
  • the horizontal axis is the thickness dCL (nm) of each InGaN layer CL.
  • the vertical axis is the relative EL intensity Intl at the wavelength of 550 nm.
  • data is shown for a semiconductor light emitting element 119d according to a reference example, in addition to data for semiconductor light emitting elements 112c and 112d according to this embodiment.
  • the In composition ratio ya of the p-side InGaN layer CLa and the In composition ratio yb of the n-side InGaN layer CLb are each 0.01. Apart from this, the configuration is the same as that of the semiconductor light emitting element 111b. In the semiconductor light emitting element 112d, the In composition ratio ya of the p- side InGaN layer CLa and the In composition ratio yb of the n-side InGaN layer CLb are each 0.05, and apart from this, the configuration is the same as that of the semiconductor light emitting element 112c.
  • the In composition ratio ya of the p-side InGaN layer CLa and the In composition ratio yb of the n-side InGaN layer CLb are each 0, and apart from this, the configuration is the same as that of the semiconductor light emitting element 112c.
  • the relative EL intensity of the light emitting layer EL is higher than that of the semiconductor light emitting element 119d that does not include the InGaN layer CL.
  • the In composition ratio y of the InGaN layer CL is low at 0.01.
  • the relative EL intensity is high, even when the thickness of each InGaN layer CL is 2 nm.
  • the In composition ratio y of the InGaN layer CL is 0.05, which is higher than that of the semiconductor light emitting element 112c.
  • the relative EL intensity is lower than that of the semiconductor light emitting element 119d.
  • the In composition ratio y is high at 0.05, preferably, the thickness of each InGaN is less than 2 nm.
  • FIG. 8 is a graph showing the characteristics of a semiconductor light emitting element.
  • FIG. 8 shows the relative EL intensity of a semiconductor light emitting element 112e according to this embodiment when the thickness dSL of the intermediate layer SL is varied.
  • the horizontal axis is the thickness dSL (nm) of the intermediate layer SL.
  • the vertical axis is the relative EL intensity Intl at the wavelength of 550 nm.
  • the thickness dSL of the intermediate layer SL is equivalent to the distance between the well layer WL1 and the AIGaN layer ML.
  • the Al composition ratio x in the AIGaN layer ML is 0.3. Apart from this, the configuration is the same as that of the semiconductor light emitting element 111b.
  • the thickness dSL of the intermediate layer SL is not less than 1 nm, the relative EL intensity is reduced.
  • the thickness dSL of the intermediate layer SL is, for example, not more than 2 nm.
  • the thickness dSL of the intermediate layer SL is, for example, not more than 1 nm.
  • the intermediate layer SL may not be provided.
  • FIGS. 9A to 9D are graphs showing the characteristics of a semiconductor light emitting element according to the first embodiment.
  • FIGS. 9A to 9D show examples of the luminous intensity when the Al composition ratio x of the AIGaN layer ML included in the light emitting layer EL is varied.
  • the horizontal axis is the peak wavelength ⁇ (nm) in each case.
  • the vertical axis is the luminous intensity Int2.
  • data is shown for a semiconductor light emitting element 119e that does not include the AIGaN layer ML.
  • the Al composition ratio x of the AIGaN layer ML is 0.09. Apart from this, the configuration is the same as that of the semiconductor light emitting element 111b.
  • the Al composition ratio x of the AIGaN layer ML is 0.13, and apart from this, the configuration is the same as that of the semiconductor light emitting element 113a.
  • the Al composition ratio x of the AIGaN layer ML is 0.18, and apart from this, the configuration is the same as that of the semiconductor light emitting element 113a.
  • the Al composition ratio x of the AIGaN layer ML is 0.30, and apart from this, the configuration is the same as that of the semiconductor light emitting element 113a.
  • the luminous intensity is lower than that of the semiconductor light emitting element 119e.
  • the semiconductor light emitting elements 113c and 113d the luminous intensity is higher than that of the semiconductor light emitting element 119e.
  • the Al composition ratio is, for example, set appropriately in accordance with the peak wavelength ⁇ .
  • the Al composition ratio x is not less than 0.25 and not more than 0.6.
  • the Al composition ratio x is not less than 0.3 and not more than 0.8.
  • the Al composition ratio x is not less than 0.4 and not more than 1.
  • FIG. 10 is a graph showing the characteristics of the semiconductor light emitting element according to the first embodiment.
  • FIG. 10 shows an example of the relative luminous intensity in a semiconductor light emitting element 114a when the In composition ratio y in each InGaN layer CL (p-side InGaN layer CLa and n-side InGaN layer CLb) in the light emitting layer EL is varied.
  • the horizontal axis is the In composition ratio y in each InGaN layer CL.
  • the vertical axis is the relative luminous intensity Int3 at the wavelength of 550 nm.
  • the Al composition ratio x of the AIGaN layer ML included in the light emitting layer EL is 0.25.
  • the thicknesses of the p-side InGaN layer CLa and the n-side InGaN layer CLb are each 1 nm.
  • the configuration apart from this is the same as that of the semiconductor light emitting element 111b.
  • the relative luminous intensity is increased by providing the InGaN layer. If the In composition ratio y in each InGaN layer CL is greater than 0.1, the effect of providing the InGaN layer CL is reduced.
  • the In composition ratio y in each InGaN layer CL is, for example, greater than 0 and not more than 0.1.
  • the In composition ratio y in each InGaN layer CL is, for example, not less than 0.002 and not more than 0.05.
  • the In composition ratio y in each InGaN layer CL is, for example, not less than 0.003 and not more than 0.03. Thereby, high efficiency can be obtained.
  • FIG. 11 is a graph showing the characteristics of the semiconductor light emitting element according to the first embodiment.
  • FIG. 11 shows an example of the relative EL intensity in semiconductor light emitting elements 114b and 114c when the In composition ratio y in each InGaN layer CL (p-side InGaN layer CLa and n-side InGaN layer CLb) in the light emitting layer EL is varied.
  • the horizontal axis is the In composition ratio y in each InGaN layer CL.
  • the vertical axis is the relative EL intensity Intl at the wavelength of 580 nm.
  • the Al composition ratio x of the AIGaN layer ML included in the light emitting layer EL of the semiconductor light emitting element 114a is 0.25.
  • the total of the thicknesses of the p-side InGaN layer CLa and the n-side InGaN layer CLb is 2 nm.
  • the configuration apart from this is the same as that of the semiconductor light emitting element 111b.
  • the total of the thicknesses of the p-side InGaN layer CLa and the n-side InGaN layer CLb is 3 nm, and apart from this, the configuration is the same as that of the semiconductor light emitting element 114b.
  • the efficiency is high.
  • the Al composition ratio x and the In composition ratio y can be measured by a method such as energy dispersive x-ray spectrometry (EDX) or the like.
  • EDX energy dispersive x-ray spectrometry
  • a structure analysis method using a secondary ion microprobe mass spectrometer (SIMS) or an omega-2 theta scan using an x-ray diffraction device can be used.
  • the thickness of crystal layers such as the AIGaN layer ML, the InGaN layer CL or the like can be obtained from, for example, an electron microscope photographic image of a cross-section of the crystal layer, or the like.
  • the AIGaN layer ML is, for example, in layer form.
  • the InGaN layer CL may be in layer form, or may be in mesh form. In the mesh form, openings are provided. If the InGaN layer CL is in layer form, for example, the high-efficiency effect as described above is easily obtained. If the InGaN layer CL is in mesh form, for example, the high efficiency effect as well as a reduction in operating voltage effect are easily obtained.
  • This embodiment relates to a method for manufacturing the semiconductor light emitting element.
  • the method for manufacturing the semiconductor light emitting element 111 as already described or the like can be applied.
  • FIG. 12 is a flowchart illustrating a manufacturing method of a semiconductor light emitting element according to the second embodiment.
  • the method for manufacturing the semiconductor light emitting element includes a process of forming the first well layer WLl in contact with the n-side barrier layer BLN provided on the n-type semiconductor layer 10 which includes semiconductor nitride (step S110). In this process, the first well layer WLl is formed at a first temperature Tl.
  • This manufacturing method further includes a process of forming the first AIGaN layer ML1 on the first well layer WLl, including Al x iGai- x iN (0.15 ⁇ xl ⁇ l) (step S120). In this process, the first AIGaN layer ML1 is formed at a second temperature T2.
  • This manufacturing method further includes a process of forming the first p-side InGaN layer CLal on the first AIGaN layer ML1, including In ya iGai-yaiN (0 ⁇ yal ⁇ 0.1) (step S130). In this process, the first p-side InGaN layer CLal is formed at a third temperature T3.
  • This manufacturing method further includes a process of forming the first barrier layer BL on the first p-side InGaN layer CLal(step S140). In this process, the first barrier layer BL1 is formed at a fourth temperature T4.
  • the fourth temperature T4 is, for example, higher than the first temperature Tl.
  • the difference between the fourth temperature T4 and the first temperature Tl is, for example, not less than 50°C.
  • the second temperature T2 is, for example, the same as the fourth temperature T4.
  • the third temperature T3 is, for example, the same as the fourth temperature T4.
  • the first temperature Tl is, for example, not less than 700°C and not more than 800°C.
  • the second temperature T2, the third temperature T3, and the fourth temperature T4 are, for example, not less than 50°C higher than the first temperature Tl.
  • the second temperature T2, the third temperature T3, and the fourth temperature T4 are, for example, not less than 810°C and not more than 905°C.
  • the second temperature T2, the third temperature T3, and the fourth temperature T4 are, for example, not less than 860°C and not more than 890°C.
  • the manufacturing method according to this embodiment it is possible to provide a method for manufacturing a semiconductor light emitting element with high efficiency.
  • FIG. 13A and FIG. 13B are schematic views illustrating a semiconductor light emitting element according to a third embodiment.
  • FIG. 13A is a schematic cross-sectional view illustrating a semiconductor light emitting element 115 according to this embodiment.
  • the n-type semiconductor layer 10, the p-type semiconductor layer 20, and the light emitting unit 30 are provided in the semiconductor light emitting element 115.
  • the n-side barrier layer BLN and the light emitting layer EL are provided in the light emitting unit 30.
  • the well layer WL, the AIGaN layer ML, the n-side InGaN layer CLb, the p-side InGaN layer CLa, and the barrier layer BL are provided in the light emitting layer EL. These layers are stacked in sequence.
  • the configurations and materials described for the first embodiment are applied to the n-type semiconductor layer 10, the p-type semiconductor layer 20, the n-side barrier layer BLN, the well layer WL, the n-side InGaN layer CLb, the p-side InGaN layer CLa, and the barrier layer BL.
  • the Al composition ratio x in the AIGaN layer ML is 0.5 ⁇ x ⁇ l.
  • FIG. 13B is a transmission electron microscope photographic image of a cross-section parallel to the Z-axis direction of the light emitting layer EL.
  • the portions where the concentration (brightness) is high corresponds to the well layer WL.
  • the portions where the concentration is low corresponds to the AIGaN layer ML.
  • the portion with the intermediate concentration between the i-th AIGaN layer ML and the (i+l)-th well layer WL(i+l) corresponds to the i-th barrier layer BLi, the i-th p-side InGaN layer CLai, and the i-th n-side InGaN layer CLb ("i" is an integer 1 or greater).
  • Irregularities are formed on the well layer WL, so the thickness of the well layer WL varies spatially.
  • the upper surface WLui of the i-th well layer WLi (for example, the surface of the first well layer WLI on the first AIGaN layer side) has irregularities.
  • the AIGaN layer ML also has irregularities, and the thickness of the AIGaN layer ML varies spatially (there are fluctuations in the thickness).
  • the upper surface MLui of the i-th AIGaN layer MLi (for example, the surface of the first AIGaN layer ML1 on the first p-side InGaN layer CLal side) has irregularities.
  • FIG. 13B light and shade can be seen in the portion of the image corresponding to the AIGaN layer ML.
  • average information for the depth direction of the test material can be seen. Therefore, the light and shade of the image in the transmission electron microscope photograph reflects the variation in the thickness.
  • the upper surface CLui of the i-th InGaN layer CLi (for example, the surface of the first p-side InGaN layer CLal on the first barrier layer BL1 side) is flatter than the surface MLui.
  • the InGaN layer CL is, for example, in layer form.
  • FIGS. 14A to 14F are schematic views illustrating the semiconductor light emitting element according to this embodiment.
  • FIGS. 14A to 14F are atomic force microscope (AFM) images of test material after forming the first AIGaN layer ML1, and before forming the other layers of the light emitting layer EL.
  • AFM atomic force microscope
  • FIGS. 14A to 14C correspond to the semiconductor light emitting elements 115a, 115b, and 112a, respectively.
  • the configuration as described for the semiconductor light emitting element 115 is applied to the semiconductor light emitting elements 115a and 115b.
  • the Al composition ratios x of the AIGaN layer ML are 0.9, 0.5, and 0.3, respectively.
  • the first AIGaN layer ML1 is, for example, formed by step flow growth. Apart from the AIGaN layer ML, the same configurations have been applied to the semiconductor light emitting elements 115a, 115b, and 112a.
  • speckled light and shade can be seen on the surface of the first AIGaN layer ML1.
  • This speckled light and shade corresponds to steps on the surface of the first AIGaN layer ML1.
  • the magnitude (light and shade) of the steps corresponds to the number corresponding to the number of atomic steps in forming the film (magnitude of irregularities).
  • the surfaces of the first AIGaN layer ML1 of the semiconductor light emitting elements 115a and 115b have irregularities.
  • the root mean square (RMS) of the variation in the thickness of the AIGaN layer ML in the semiconductor light emitting element 115a is, for example, about 2.2 nm.
  • the RMS of the variation in the thickness of the AIGaN layer ML in the semiconductor light emitting element 115b is, for example, about 1.6 nm.
  • the semiconductor light emitting element 112a shown on FIG. 14C there is little light and shade in the image.
  • the surface of the first AIGaN layer ML1 in the semiconductor light emitting element 112a is flatter than the surface of the first AIGaN layer ML1 in the semiconductor light emitting elements 115a and 115b.
  • the RMS of the variation in the thickness of the first AIGaN layer ML1 in the semiconductor light emitting element 112a is smaller than the RMS of the variation in the thickness of the first AIGaN layer ML1 in the semiconductor light emitting element 115a.
  • the RMS of the variation in the thickness of the first AIGaN layer ML1 in the semiconductor light emitting element 112a is about 0.5 nm.
  • the RMS of the variation in the thickness of the first AIGaN layer ML1 is large when, for example, the Al composition ratio xl of the first AIGaN layer ML1 is not less than 0.5.
  • FIGS. 14D to 14F are AFM images observing the surface of the first barrier layer BL1, after the first AIGaN layer ML1 has been formed, and after the other layers of the first light emitting layer ELI (first n-side InGaN layer CLbl, first p-side InGaN layer CLal, first barrier layer BL1, and the like.) have been formed.
  • first n-side InGaN layer CLbl, first p-side InGaN layer CLal, first barrier layer BL1, and the like. have been formed.
  • FIGS. 14D to 14F correspond to the semiconductor light emitting elements 115a, 115b, and 112a, respectively.
  • FIGS. 14A and 14D By comparing FIGS. 14A and 14D, and comparing FIGS. 14B and 14E, it can be seen that the surface of the first barrier layer BLl is very flat compared with the surface immediately after the first AIGaN layer ML1 is formed thereon.
  • FIGS. 14D and 14E there are fewer high concentration points (dark points) than in FIG. 14F. These points indicate holes in the first barrier layer BLl, for example.
  • the surface of the first barrier layer BLl of the semiconductor light emitting element 115a and the surface of the first barrier layer BLl of the semiconductor light emitting element 115b are flatter than the surface of the first barrier layer BLl of the semiconductor light emitting element 112a.
  • the surface of the first barrier layer BLl of the semiconductor light emitting element 115a and the surface of the first barrier layer BLl of the semiconductor light emitting element 115b have a step and terrace structure.
  • the RMS of the variation in the thickness of the first barrier layer BLl in the semiconductor light emitting element 115a is about 0.2 nm.
  • the RMS of the variation in the thickness of the first barrier layer BLl in the semiconductor light emitting element 115b is about 0.3 nm.
  • the RMS of the variation in the thickness of the first barrier layer BLl in the semiconductor light emitting element 112a is about 0.6 nm.
  • the surface of the p-type semiconductor layer 20 side of the first barrier layer BLl is flatter than the surface of the first p-side InGaN layer CLal side of the first AIGaN layer NL1.
  • the first well layer WL1 in some cases, irregularities are formed on the surface of the first well layer WLl.
  • the irregularities formed on the surface of the first well layer WLl are filled up so that depressions are filled by the first AIGaN layer ML1 (for example, Al composition ratio x is not less than 0.5) which has large variation in the thickness.
  • the flatness of the first InGaN layer CLl and the flatness of the first barrier layer BL1 formed thereupon are improved.
  • the holes observed in the surface of the first barrier layer BL1 are fewer.
  • the surface of the first p-side InGaN layer CLal on the first barrier layer BL1 side is flatter than the surface of the first AIGaN layer ML1 on the first p-side InGaN layer CLal side.
  • the variation in the thickness of the first well layer WLl is greater than the variation in the sum of the thickness of the first well layer WLl and the thickness of the first AIGaN layer ML1. In other words, the variation in the thickness of the first well layer WLl is greater than the variation in distance between the n-side barrier layer BLN and the first p-side InGaN layer CLal.
  • the InGaN layer CL of the semiconductor light emitting element 115b is, for example, formed in a layer form.
  • the variation in the thickness of the light emitting layer EL is suppressed.
  • the variation in the thickness of the light emitting layer EL is smaller than the variation in the thickness of the AIGaN layer ML.
  • the RMS of the variation in the thickness of the first AIGaN layer ML1 may be greater than the average value of the thickness of the first AIGaN layer ML1.
  • the first AIGaN layer ML1 may include a plurality of portions that include AIGaN that are separated from each other. In other words, the first AIGaN layer ML1 may be formed in an island form. At least one portion of the plurality of portions that are separated from each other has a width of, for example, not less than 10 nm and not more than 200 nm, in at least one direction perpendicular to the Z-axis direction. For example, if the Al composition ratio x is not less than 0.5, the AIGaN layer ML may be in island form, for example.
  • the layer below the first AIGaN layer MLl for example, the first well layer WL1
  • the layer above the first AIGaN layer MLl for example, the first InGaN layer CLl
  • the crystal quality of the light emitting layer EL is improved.
  • FIG. 15 is a graph showing the characteristics of semiconductor light emitting elements.
  • FIG. 15 is a graph in which data for the semiconductor light emitting element 115b is added to FIG. 4.
  • the Al composition ratio x of the AIGaN layer ML of the semiconductor light emitting element 115b is 0.9.
  • the reduction in output OP when the peak wavelength ⁇ is long is suppressed.
  • the peak wavelength ⁇ is not less than 570 nm, the suppression of the reduction in the luminous efficiency is significant.
  • the first AIGaN layer MLl is formed with a high
  • the first InGaN layer CLl is formed in layer form on the first AIGaN layer MLl. In this way, the crystal quality of the light emitting layer EL is improved, and the luminous efficiency at longer wavelengths is increased.
  • FIG. 16 is a graph showing the characteristics of a semiconductor light emitting element.
  • FIG. 16 shows the operating voltage Vop in the semiconductor light emitting element 112a and the semiconductor light emitting element 115b.
  • the Al composition ratio x of the AIGaN layer ML is 0.3.
  • the Al composition ratio x of the AIGaN layer ML is 0.9.
  • the horizontal axis is current (mA).
  • the vertical axis is operating voltage Vop (V).
  • the operating voltage of the semiconductor light emitting element 115b is lower than the operating voltage of the semiconductor light emitting element 112a.
  • AIGaN layer MLl is large, the area of the interface between the first AIGaN layer MLl and the first well layer WL1 becomes larger.
  • the interface area is large, for example, the area over which current flows becomes large.
  • the AIGaN layer ML is formed in island form, current can easily flow between each of the portions (each island) that include AIGaN and that are separated from each other. In this way, for example, in the semiconductor light emitting element 115b, it is considered that a low operating voltage can be obtained.
  • the first InGaN layer CL1 which has a high In composition ratio y either contacts or is close to the first AIGaN layer MLl, which has a high Al composition ratio x.
  • the difference in the lattice constant of the first InGaN layer CL1 and the lattice constant of the first AIGaN layer MLl is large.
  • a large strain is produced in the first AIGaN layer MLl.
  • a large electric field is generated in the first AIGaN layer MLl.
  • a triangular potential is produced in the first AIGaN layer ML1, which produces a mirror image effect. As a result, for example, current can easily flow.
  • the first AIGaN layer ML1 is provided approaching the first well layer WL1.
  • the reduction in the luminous efficiency due to the quantum confined Stark effect is suppressed.
  • the Al composition ratio x of the AIGaN layer ML is not less than 0.5, the luminous efficiency at yellow or red wavelengths is improved.
  • the operating voltage of the semiconductor light emitting element may be increased too much.
  • the semiconductor light emitting element 115b the operating voltage can be reduced by increasing the variation in the thickness of the AIGaN layer ML.
  • the AIGaN layer ML By forming the AIGaN layer ML with a high Al composition ratio x and a large variation in thickness, the luminous efficiency at longer wavelengths is improved, so it is possible to provide a semiconductor light emitting elements with a lower operating voltage.
  • a highly efficient semiconductor light emitting element and method for manufacturing the same can be provided.
  • nitride semiconductor includes semiconductors of all compositions wherein composition ratios of x, y, and z of the formula B x InyAl z Gai-x-y -z N fall within the respective ranges of 0 ⁇ x ⁇ l, 0 ⁇ y ⁇ l, 0 ⁇ z ⁇ l, and x+y+z ⁇ l.
  • “nitride semiconductors” shall also be understood to include semiconductors further containing class V elements other than N (nitrogen), semiconductors further containing various elements added to control various physical characteristics such as conductivity type and the like, and semiconductors further containing various elements that are included unintentionally.
  • perpendicular and “parall el” refer to not only strictly perpendicular and strictly parallel bu t also include, for example, the fluctuation due to manufacturing processes, etc. It is sufficient to be substantially perpendicular and substantially parallel.
  • Embodiments of the invention with reference to examples were described above. However, the embodiments of the invention are not limited to these examples.
  • the scope of the invention includes all cases in which, for example, a person skilled in the art could make use of publicly known information to appropriately select constituents such as the n-type semiconductor layer, p-type semiconductor layer, light emitting unit, light emitting layers, well layers, barrier layers, AIGaN layer, InGaN layer, intermediate layer, nitride semiconductor, electrodes and the like included in the semiconductor light emitting element provided that the obtained effects are similar.

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Abstract

L'invention porte sur un élément électroluminescente (110, 11) qui comprend une couche de semi-conducteur au nitrure de type n (10), une couche de semi-conducteur au nitrure de type p (20) et une unité électroluminescente (30). L'unité électroluminescente est disposée entre la couche de semi-conducteur de type n et la couche de semi-conducteur de type p, l'unité électroluminescente émettant une lumière présentant une longueur d'onde de pic non inférieure à 530 nm. L'unité électroluminescente comprend une couche de barrière côté n (BLN) et une première couche électroluminescente (EL1). La première couche électroluminescente (EL1) comprend une première couche de barrière (BL1) disposée entre la couche de barrière côté n (BLN) et la couche de semi-conducteur de type p, une première couche de puits (WL1) en contact avec la couche de barrière côté n (BLN) entre la couche de barrière côté n (BLN) et la première couche de barrière (BL1), une première couche AlGaN (ML1) comprenant Alx1Ga1_x1N (0,15≤x1≤1) disposée entre la première couche de puits (WL1) et la première couche de barrière (BL1), et une première couche InGaN côté p (CLa1) comprenant Inya1Ga1 -ya1N (O<ya1<0,1) disposée entre la première couche AlGaN (ML1) et la première couche de barrière (BL1).
PCT/JP2014/069269 2013-07-17 2014-07-15 Élément électroluminescent à semi-conducteurs à couche active de puits quantique et son procédé de fabrication WO2015008871A1 (fr)

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